What’s Vulnerable › Vulnerabilities

CVE-2026-54428: Apache HttpComponents Core: HPackDecoder Unlimited Header List Size Before SETTINGS ACK

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-01 · updated 2026-10-25
• Weakness: CWE-400

Description

Allocation of resources without limits or throttling in the HTTP/2 HPACK decoder in Apache HttpComponents Core (5.4.2 and earlier, 5.5-beta1 and earlier) allows an remote attacker to cause a denial of service through memory exhaustion by sending oversized compressed header blocks before the HTTP/2 SETTINGS acknowledgement causes the configured header list size limit to be applied.

Affected products

• Apache Software Foundation Apache HttpComponents Core: from 5.0 through 5.4.2; 5.5-alpha1, 5.5-beta1

References

• https://lists.apache.org/thread/5zjp8vczvxq19pw2rvhs21q446bhl0sd
• http://www.openwall.com/lists/oss-security/2026/07/01/3

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